The invention relates in general to wireless communication systems and more specifically to management of communication resources in wireless communication systems having overlapping service areas.
Base stations in cellular communication systems provide communications services to wireless communication devices within geographical cells where each base station exchanges signals with wireless communication devices within an associated cell. The size and shape of each cell and, therefore, the coverage area of the base station are determined by several factors and are at least partially based on design parameters of the base station. In addition to large macro cells that provide services to numerous devices within relatively large geographical areas, some cellular communication systems are increasingly employing smaller cells to increase efficiency, improve coverage, improve the quality of service, and provide additional services. The smaller cells may include a variety of sizes typically referred to as microcells, picocells and femtocells. Microcells and picocells are often implemented within office buildings, shopping centers and urban areas in order to provide additional security, higher user capacity for the area, additional service features, and/or improved quality of service. Femtocells have relatively smaller geographical areas and are typically implemented at residences or small office locations. Since typical cellular backhaul resources may not be available in these locations, femtocells are sometimes connected to the cellular infrastructure through DSL or cable modems. Femtocells are part of the cellular network and, therefore, communicate with the wireless devices using the same techniques as those used by macrocells. The proximity of the various base stations and wireless communication devices operating on the same frequency channel often results in interference. Interference can occur within the uplink channel as shown in FIG. 1A or in the downlink channel as shown in FIG. 1B. In FIG. 1A and FIG. 1B, a large service area (LSA) communication node (base station) 10 provides wireless service within an LSA 12 and a small service area (SSA) communication node (base station) 14 provides wireless service within an SSA 16. The SSA 16 and the LSA 12 at least partially overlap. In FIG. 1A and FIG. 1B, the SSA 16 is within the LSA 12. The communication nodes 10, 14 provide wireless service to mobile wireless communication devices 18, 20, sometimes referred to user equipment (UE) within their respective service areas. A SSA UE (SUE) 18 receives service from the SSA communication node 14 and an LSA UE (LUE) 20 receives service from the LSA communication node 10. As shown in FIG. 1A, the LUE 20 transmits uplink signals 22 to the LSA communication node 10 and the SUE transmits uplink signals 24 to the SSA communication node 14. When the LUE 20 and the SUE 18 use the same frequency for transmitting uplink signals 22, 24 at the same time, the LSA uplink signal 22 causes interference at the SSA communication node 14 by interfering with the SSA uplink signal 24. In addition, interference can also occur at the LSA communication node 10 due to the uplink signal 24 transmitted by the SUE 18. As shown in FIG. 1B, the LSA communication node transmits downlink signals 26 to the LUE 20 and the SSA communication node transmits downlink signals 28 to the SUE 18. When the LSA and SSA communication nodes use the same frequency for transmitting downlink signals at the same time, the SSA downlink signal causes interference at the LUE by interfering with the LSA downlink signal. Interference may also result from the LSA downlink signal 26 at the SUE. Interference is particularly significant if the LUE 20 is operating near the SSA communication node 14 due to the strong uplink and downlink signals and there is no coordination between the LSA communication node 10 and the SSA communication node 14.